Crude oils from around the world are processed at the refinery to produce a variety of products, such as gasoline, diesels, jet fuel, and asphalt. The demand for transportation fuels are increasing around world and transportation fuels are the profitable products of refiners. There is a growing drive to cost-effectively maximize production of more valuable, lighter fuel products from heavy portions of every barrel of crude oil processed. For each barrel of crudes processes 10-20 wt % will leave as heavy bottoms and may be blended as heating fuels boiler fuels, which are low value fuels.
Biomass is a renewable energy resources. There is a general consensus in the scientific community that the amount of biomass that could be grown globally on a sustainable basis is comparable to the annual world-wide consumption of energy by the transportation sector. Biomass includes agricultural residues, forestry wastes, wood process wastes, and the organic fraction of municipal solid wastes. Different methods for conversion of biomass to liquid fuels were reported in the literature. The main thermochemical routes includes gasification followed by Fischer-Tropsch synthesis, pyrolysis and direct liquefaction. The gasification of biomass is a process that converts biomass into carbon monoxide and hydrogen and possibly carbon dioxide and hydrocarbon molecules such as methane. The mixture of carbon monoxide and hydrogen can be synthesized to hydrocarbon fuels and chemicals via the well-known Fischer-Tropsch method. Pyrolysis thermally decomposes dry biomass to bio-oil in a rapid heating rate to a high temperature (400-1000° C.) in the absence of oxygen. Its liquid yield can reach up to 50-70%[1, 2]. The liquid oil of fast pyrolysis consists of 20-25% water while the remainder is mostly lighter organic compounds with high oxygen content. Pyrolysis oil has low-heating value and is about half of that of crude oils[2]. Direct liquefaction operates at mild temperatures (200-450° C.) but at high pressures (>1 MPa) for a longer residence time (10-60 min)[3-5]. It has the potential for producing heavy liquid oils with increased heating values. One advantage of direct liquefaction is the ability to convert wet biomass into energy while pyrolysis deals with dry biomass only. But direct liquefaction generates a relatively low yield of liquid fuels. The biofuels derived from both pyrolysis and liquefactions are required further upgrading before they can be blended with transportation fuels.
The cost of transportation fuels produced from lignocellulosic biomass, however, is currently not competitive with the cost fuels derived from petroleum. It is imperative to develop new processes for converting biomass to biofuels that involve less number of process steps so that both the capital and operating expenses associated are reduced.